Hydraulic power transmission apparatus



Oct. 9, 1962 N. LEE

HYDRAULIC POWER TRANSMISSION APPARATUS 3 Sheets-Sheet 1 Filed June 8, 1961 INVENTOR NORMAN LEE BY a ywflyflii {0%,

ATTQRNEH Oct. 9, 1962 N. LEE

HYDRAULIC POWER TRANSMISSION APPARATUS 3 Sheets-Sheet 2 Filed June 8, 1961 lNvENToR NQQMRN LEE Oct. 9, 1962 N. LEE 3,057,162

HYDRAULIC POWER TRANSMISSION APPARATUS Filed June 8, 1961 5 Sheets-Sheet 3 \NVENTOQ NORMAN LEE ATroeNEY mite This invention relates to hydraulic power transmission apparatus of the kind comprising a power-driven displacement pump (hereinafter for convenience called the main pump) arranged to draw fluid from an inlet passage and deliver it to a delivery passage, at least one hydraulic motor of the displacement type the inlet passage of which is connected to the pump delivery passage while its exhaust passage is connected directly, or through a reservoir, to the pump inlet passage, and control means arranged to be sensitive to a signal derived from sensing apparatus which is influenced by a condition dependent directly or indirectly on the speed and/or torque of the motor and to control the volumetric rate of delivery of fluid to the inlet passage of the motor in a manner tending to cause the motor to operate at a determined speed and/or torque, for example at a speed and/or torque which is automatically varied progressively in accordance with some predetermined function, such for example as the effective diameter of a drum driven by the motor and on to Which a length of material, for example strip or wire, is being wound.

In hydraulic power transmission apparatus of the kind referred to and in which the motor drives a drum on to which a length of material is to be wound, it has been proposed to provide torque-sensitive apparatus in the form of a jockey roller bearing on a free length of the material which is being wound on to and thus maintained in tension by the drum, the jockey roller being arranged as it moves with variations in tension to transmit a signal to relay apparatus which acts on control apparatus by which the output of the main pump is varied in the appropriate sense so as to keep the tension within predetermined limits. Such apparatus, however, is not sufliciently sensitive for some applications, that is to say the required changes in the pump output cannot be effected sufliciently rapidly upon movement of the jockey roller or the like to maintain the tension in the material within sufliciently small limits. It is an object of the present invention to provide hydraulic power transmission apparatus of the kind referred to, applicable not only to apparatus in which the hydraulic motor drives a drum as above described, but also to other apparatu where it is desired to maintain Within close determined limits the torque and/or speed of the hydraulic motor, in which the control will be more sensitive than in apparatus in which the control is effected solely by varying the output of the main pump.

Hydraulic power transmission apparatus according to the present invention comprises a main power driven pump of the displacement type arranged to draw fluid from a main pump inlet passage and deliver it to a main pump delivery passage, at least one hydraulic motor of the displacement type arranged to drive the driven apparatus, the inlet and outlet ports of which motor are connected respectively to the delivery passage of the main pump and to an exhaust passage communicating directly, or through a reservoir, with the main pump inlet passage, ratio-control mechanism by which the capacity of the pump and/or motor can be changed to vary the torque applied by the motor to the driven apparatus sensing apparatus arranged to be influenced directy or indirectly by a condition or conditions dependent directly or indirectly upon the torque applied by the motor to 3,fl57,162 Patented Oct. 9, 1952 the driven apparatus, an auxiliary source of fluid under pressure (herein called the control fluid) arranged to deliver control fluid through an auxiliary delivery passage into the main pump delivery passage, control valve apparatus arranged to control the volumetric rate of delivery of the control fluid into the main pump delivery passage in accordance with signals derived from the sensing apparatus, and further control means influenced directly or indirectly in accordance with factors associated with the volumetric rate of delivery of control fluid and arranged to cause adjustment of the ratio-control mechanism in the required sense when such volumetric rate of delivery passes outside a determined flow range.

Preferably the said further control means when brought into operation acts to cause an adjustment of the ratiocontrol mechanism such as to bring the volumetric rate of delivery of control fluid back to a value which is substantially removed from both ends of the determined flow range, that is to say so as to bring the control valve apparatus back into a position approaching its neutral position.

In one arrangement according to the invention, the said further control means comprises at least one flow sensitive device arranged to be influenced by the volumetric rate of flow of the control fluid, and relay apparatus arranged to be brought into operation by said device in one direction or the other dependent on whether the flow rate approaches the upper or lower end of the determined flow range. Such a flow sensitive device may be arranged to be subject to a difierential pressure dependent on the volumetric rate of flow of the control fluid, for example to the pressure on the two sides respectively of a restriction arranged in a passage through which the control fluid flows.

In an alternative arrangement according to the invention said further control means may comprise a flow sensitive device arranged to transmit a signal in accordance with the rate of flow of control fluid irrespective of the direction of said flow and to bring into operation a servo motor operating the ratio-control mechanism when said signal exceeds a predetermined value, and a selector device operated by the valve apparatus to select the direction in which the servo motor then is caused to operate in accordance with the position of said valve apparatus to one side or the other of its neutral position.

In a still further arrangement according to the invention the said further control means may comprise apparatus arranged to be sensitive to the relationship between the speed of the motor and the setting of the ratiocontrol mechanism and to bring into operation a servo motor operating the ratio control mechanism when the relationship referred to becomes such as occurs when the volumetric rate of flow of control fluid approaches one end or the other of the determined flow range.

The invention may be carried into practice in various Ways but three alternative ways in which the invention may be put into practice are shown diagrammatically in the accompanying drawings, in which FIGURE 1 shows one arrangement according to the invention,

FIGURE 2 shows a second arrangement according to the invention, and

FIGURE 3 shows a third arrangement according to the invention.

In each of the arrangements diagrammatically shown in the drawings the apparatus comprises a pump 1 of the displacement type arranged to be driven by a motor, indicated as an electric motor at 2, the pump being of the type in which the capacity (that is to say the volume of liquid delivered by the pump for each revolution) can be varied in known manner by means of a lever indicated at 3 the capacity being increased by movement of this lever 3 in the direction of the arrow marked with the plus sign and decreased by movement of the lever 3 in the direction of the arrow marked with the minus sign. The pump 1 is arranged to deliver working fluid into a main delivery passage 4 by which such fluid is delivered to the inlet 5 of a hydraulic motor 6 also of the displacement type, the outlet passage 7 of which also constitutes the inlet passage to the pump 1. Generally a reservoir for working fluid will be included in the passage 7 as indicated at 7a in generally known manner.

The motor 6 is arranged to drive driven mechanism comprising, in the example shown, a reel 8 on to which is to be wound a web 9, for example of paper, which as shown is led under two guide rollers 10 and over a jockey roller 11 situated between them so that the jockey roller is subject to a downward forc dependent on the tension in the web 9.

The jockey roller 11 thus constitutes a sensing device responsive to a force dependent on the tension in the Web 9 and hence dependent on the torque applied by the motor 6 to the reel 8. In the examples diagrammatically shown the jockey roller 11 is mounted upon the end of the rod 12 of a control valve by which the flow of fluid, herein called control fluid, to the delivery passage 4 of the pump 1 through a control fluid delivery passage 13 and from the outlet passage 7 of the motor 6 through a control fluid outlet passage 14, is controlled.

The control valve comprises a casing 15 and a valve member, generally indicated at 16, operated by the rod 12. The casing 15 is provided in its bore with an approximately central inlet annulus 17, to which control fluid is delivered through a delivery passage 17a from an auxiliary source of fluid comprising a continuously driven pump 18 and a reservoir 19, and with a pair of outlet annuli 20 equally displaced on opposite sides of the inlet annulus 17 and Communicating with the reservoir 19 through a return flow passage 21. The valve 16 has three-lands 22, 23, 24 which in the neutral position of the valve close the annuli 17 and 20, and the passage 13 opens into the bore of the housing 15 between the lands Hand 23 while the passage 14 opens into such bore between the lands 23 and 24, so that on movement of the valve member 16 upwards or downwards the passage 13 or 14 will be connected to the source of auxiliary fluid through the annulus 17 and the other of these two passages will be connected through one of the annuli 20 to the return flow passage 21. A relief valve 25 is provided in a passage 25 extending between the inlet and outlet sides of the pump 18 so as to return surpuls fluid delivered by the pump to the inlet side of the pump while maintaining a substantially constant pressure of fluid in the annulus 17.

A compression spring 26, which may be adjusted by means of an adjusting screw 27, acts on th lower end of the rod 12 of the valve 16 in a direction counteracting the force applied to the jockey roller 11 due to the tension in the. web 9.

It will be apparent that movement of the lever 3 will vary the transmission ratio as between the pump 1 and the motor 6 so as to control the torque applied by the motor 6 to the reel 8 and hence the tension in the web 9. In addition a sensitive control of the tension in the web will be effected by operation of the valve 16 under the action of the jockey roller 11, since (assuming the valve 16 to be in the position shown) any upward movement of this valve due to a decrease in the tension in the web 9 will cause the delivery passage 5 of the pump 1 to be connected through the passage 13 by the valve 16 to theannulus 17 and hence to the control fluid delivery passage 17a while the inlet passag 7 of the pump 1 will be similarly connected to the passage 21 through the appropriate annulus 20. 'Thus the flow of fluid through the motor 6 will be slightly increased to increase the tension in the web 9 again to that required. Similarly any downward movement of the valve 16 from the position shown 4 due to an increase in tension in the web 9 will permit working fluid to escape through the passage 13 to the passage 21 to reduce the tension in the Web to that desired and a corresponding flow of control fluid through the passage 14 to the inlet passage 7 of the main pump 1 to maintain the quantity of fluid in the working fluid circuit substantially unaltered.

Within the capacity for delivery of control fluid through the valve 16, therefore, the valve constitutes a sensitive control device for maintaining the required tension in the web If and when, however, this valve moves from the position shown in either direction beyond a predetermined point indicating that it is approaching the limit of the possible control of Web tension by it alone, means are provided by which an appropriate adjustment of the lever 3 is automatically caused to take place.

The adjusting mechanism for the lever '3 is in the form of a servo motor comprising a piston 28 operating within a servo cylinder 29 and acting through a piston rod and link 30 on the lever 3, the opposite ends of the cylinder 29 communicating through inlet and outlet passages 31, 32 with the bore of the housing 33 of a servo valve 34 having two lands 35, 36 which in the neutral position of the valv cover annuli communicating with the passages 31 and 32 and with upward or downward movement of the valve, bring one or other of such annuli into communication with an inlet port 37 and the other of such passages into communication with one or other of two outlet ports 38 all in a manner generally known per se. Thus upward movement of the servo valve 34 from the position shown will cause downward movement of the piston 28 to increase the capacity of the pump 1 and vice versa.

In each of the arrangements diagrammatically shown the valve 34 is arranged to be controlled by solenoids 39 and 40 so arranged that upward movement of the valve will be caused by energisation of the solenoid 39 and downward movement of the valve by energisation of the solenoid 40.

Operating fluid is supplied to the servo motor including the piston 28 by a power driven pump 41 arranged to deliver fluid through a delivery passage 42 from a reservoir 43 to which fluid returns from the ports 38 through a return passage 44, a relief valve 45 being associated with the pump 41 to permit return to the reservoir 43 of surplus fluid delivered by the pump 41.

In the arrangement shown in FIGURE 1 the solenoids 39 and 40 are arranged to be energised'respectively by the closing of two interconnected switches indicated at 46 and 47. The movable members of these switches are connected to a rod 48 which is acted upon by two flexible resilient diaphragms 49, 50 which are respectively arranged to be subject to the difference in pressures on the two sides of restrictions 51 and 52 in the passages 13 and 14.

It will be seen that when the flow through the passages 13 and 14 in either direction exceeds a predetermined value due to the valve 16 having moved from its neutral position to a predetermined extent in one direction or the other the differential pressures thus acting on the diaphragms 49 and 51} will cause the switch 46 or the switch 47 to be closed and thus cause the valve 34 to be moved either upwards or downwards to cause an appropriate adjustment of the lever 3 by the servo piston 28. Associated with the switches 46 and 47 are holding magnets indicated at 53, so that the appropriate switch will not only tend to close with a snap action after a predetermined movement of the rod 48 in one direction or the other from its central position, but will then be maintained closed until the diiferential pressures on the diaphragms 44 and 45 which caused such closing have been substantially reduced, that is to say, in a preferred case, until the lever 3 has been moved to an extent such that the valve 16 will have been restored approximately to its neutral position.

In the alternative arrangement shown diagrammatically in FIGURE 2, no restrictions are provided in the passages 13 and 14 and there is provided in the passage 14 a meter device indicated at 54, arranged to be driven by the flow of fluid through the passage 14 in whichever direction such flow takes place. The meter device 54 drives an electric generator 55 by which, whichever the direction of rotation, a signal in the form of an electric current is transmitted to the solenoid 56 of a relay switch indicated at 57. The switch 57 is arranged to control the circuits of the two solenoids 39 and 40 in cooperation with a change-over switch indicated generally at 58. The change-over switch 58 is arranged to be actuated, as indicated, by a lever 59 connected to the rod 12 of the valve 16 so that for positions of this valve displaced from its neutral position the switch 58 selects appropriately which of the two solenoids 39 and 40 shall be operated on closing of the switch 57 and hence the direction in which the adjustment of the lever 3 will then be effected by the piston 28 of the servo motor. The switch 57 has associated with it a holding magnet 80 so that it will close with a snap action and once closed will remain closed until there has been a substantial reduction in or virtual elimination of flow in the passage 14, that is to say until an appropriate adjustment has been made to the lever 3.

In the further alternative diagrammatically shown in FIGURE 3 the motor 6 drives, for example through transmission apparatus diagrammatically shown at 60, an electric signal generator 61 which transmits a signal in the form of an electric current through a rheostat 62 to a solenoid 63 arranged to operate a two-way switch 64 including a spring 65 which acts in opposition to the solenoid 63. The switch 64 has two pairs of contacts, 66 and 67, which, when closed by the switch, cause energisation respectively of the solenoid 39 or 40. The arm 82 controlling the effective resistance of the rheostat 62 is arranged to be actuated, as indicated, by the lever 3.

The arrangement operates as follows. The degree of energisation of the solenoid 63 depends upon the relationship between the speed of the generator 61, that is to say the speed of the motor 6, on the one hand, and the setting of the transmission ratio control member 3 on the other hand, and as long as the relationship between the speed of the motor 6 and the setting of the ratio control member 3 is that corresponding to there being no flow of control fluid or only a relatively small flow of control fluid through the passages 13 and 14 (that is to say to the valve 16 being either closed or only slightly open in either direction) the solenoid 63 will be energised to an intermediate extent suflicient to maintain the switch 64 in its neutral position. If and when the relationship between the speed of the motor 6 and the setting of the lever 3 becomes one which corresponds to more than a predetermined flow of fluid through the passages 13 and 14 then the energisation of the solenoid 63 will be such as to cause closure either of the contacts 66 or of the contacts 67, according to the sense in which the out-of-balance between the speed of the motor 6 and the setting of the lever 3 has occurred, whereupon the servo valve 34 will be operated to cause an adjustment of the lever 3 by the piston 28 such as to restore substantially the correct relationship between the speed of the motor 6 and the setting of the lever 3, that is the relationship at which the solenoid 63 maintains the switch 64 in its neutral position, thus also causing movement or the valve 16 towards or into its neutral position. Holding magnets 68 and 69 for the switch 64 are shown to cause snap action of the switch and to ensure that after closing it remains in its closed position until the appropriate adjustment has been made.

It will be understood that in the arrangements diagrammatically shown in the drawings direct mechanical electromagnetic and hydraulic operation has been shown for convenience only in indicating three general systems which may be adopted according to the invention, and that in practice electronic or other indirect control and operating devices may be incorporated in the apparatus. For example, the jocky roller or the equivalent may be arranged to act on a strain gauge or other load-sensitive device incorporated in an electronic system by which the signals derived from the strain gauge are amplified and applied to the valve controlling the flow of control fluid to and from the working fluid circuit.

What I claim as my invention and desire to secure by Letters Patent is:

l. Hydraulic power transmission apparatus comprising a main power driven pump of the displacement type connected to draw fluid from a main pump inlet passage and deliver it to a main pump delivery passage, at least one hydraulic motor of the displacement type connected to drive driven apparatus, inlet and outlet ports of which motor are connected respectively to the delivery passage and to the inlet passage of the main pump, a ratio-control mechanism by which the relationship between the capacity of the pump and the capacity of said motor can be changed to vary the torque applied by the motor to the driven apparatus, sensing apparatus arranged to be influenced by a change in conditions dependent upon the torque applied by the motor to the driven apparatus, an auxiliary source of fluid under pressure connected to deliver control fluid through an auxiliary delivery passage into the main pump delivery passage, a control valve responsive to said sensing apparatus arranged to control the volumetric rate of delivery of the control fluid into the main pump delivery passage, and further control means, responsive to the volumetric rate of delivery of said control fluid, to adjust said ratio-control mechanism when said volumetric rate of delivery is beyond a predetermined range.

2. Hydraulic power transmission apparatus as claimed in claim 1, in which the said further control means when brought into operation acts to cause an adjustment of the ratio-control mechanism such as to bring the volumetric rate of delivery of control fluid back to a value which is substantially removed from both ends of the predetermined flow range.

3. Hydraulic power transmission apparatus as claimed in claim 2 in which the said further control means comprises at least one flow-sensitive device arranged to be influenced by the volumetric rate of flow of the control fluid, and relay apparatus arranged to operate the ratiocontrol mechanism and to be brought into operation by said device in one direction or the other dependent on whether the flow rate approaches the upper or lower end of the predetermined flow range.

4. Hydraulic power transmission apparatus as claimed in claim 3 in which the flow-sensitive device is arranged to be subject to a differential pressure dependent on the volumetric rate of flow of control fluid.

5. Hydraulic power transmission apparatus as claimed in claim 1 in which the said further control means comprises a flow-sensitive device arranged to transmit a signal in accordance with the rate of flow of control fluid irrespective of the direction of said flow and to bring into operation a servo motor operating the ratio-control mechanism when said signal exceeds a predetermined value, and a selector device operated by the valve apparatus to select the direction in which the servo motor is caused to operate in accordance with the position of said valve apparatus to one side or the other of a neutral position.

6. Hydraulic power transmission apparatus as claimed in claim 1 in which the said further control apparatus comprise apparatus arranged to be sensitive to the relationship between the speed of the motor and the setting of the ratio control mechanism and to bring into operation a servo motor operating the ratio-control mechanism when the relationship referred to becomes such as occurs when the volumetric rate of flow of control fluid approaches one end or the other of the predetermined flow range.

7. Hydraulic power transmission apparatus as claimed in claim 1 in which the said further control means comprises at least one flow-sensitive device arranged to be influenced by the volumetric rate of flow of the control fluid, and relay apparatus arranged to operate the ratiocontrol mechanism and to be brought into operation by said device in one direction or the other, dependent on whether the fiow rate approache the upper or lower ends of the predetermined flow range.

8. Hydraulic power transmission apparatus as claimed in claim 7 in which the flow-sensitive device is arranged to be subject to a difierential pressure dependent on the volumetric rate of flow of control fluid.

9. Hydraulic power transmission apparatus as claimed in claim 2 in which the said further control means comprises a flow-sensitive device arranged to transmit a signal in accordance with the rate of flow of control fluid irrespective of the direction of said flow and to bring into operati n a servo motor operating the ratio-control mechanism when said signal exceeds a predetermined value, and a selector device operated by the valve apparatus to select the direction in which the servo motor is caused to operate in accordance with the position of said valve apparatus to one side or the other of a neutral position.

10. Hydraulic power transmission apparatus as claimed in claim 2 in which the said further control apparatus comprises apparatus arranged to be sensitive to the relationship between the speed of the motor and the setting of the ratio-control mechanism and to bring into operation a servo motor operating the ratio-control mechanism when the relationship referred to becomes such as occurs when the volumetric rate of flow of control fluid approaches one end or the other of the predetermined flow range.

References Cited in the file of this patent UNITED STATES PATENTS 2,402,789 Tweedale June 25, 1946 2,425,496 Tyler Aug. 12, 1947 FOREIGN PATENTS 1,203,759 France Ian. 21, 1960 

